ABSTRACT
Using a radioimmunoassay directed towards human proGRP (42-53) on acetic acid extracts, immunoreactivity was measured throughout the porcine GI-tract in concentrations that were parallel to those of GRP (gastrin-releasing peptide or 'mammalian bombesin'). Gel filtration and HPLC studies of human and porcine tissue extracts revealed that the immunoreactivity was mainly due to a peptide with a molecular size of 8-9 kDa. The peptide did not contain the GRP sequence, making it a major fragment of the GRP C-flanking part of proGRP. Furthermore, a peptide of similar size with proGRP (42-53) immunoreactivity was released from isolated, perfused preparations of porcine antral and non-antral stomach and pancreas in parallel with GRP in response to electrical stimulation of the vagus nerves. Our results suggest that a processing of preproGRP occurs in normal, adult human and porcine tissues, that is similar to that previously demonstrated in small cell lung carcinomas and human fetal lungs. The finding that the immunoreactive proGRP fragment is released from the tissues upon appropriate stimulation raises the question of a possible physiological role for proGRP products other than GRP.
